Fluorescent material and illumination device

ABSTRACT

A fluorescent material represented by the following formula (I):
 
M 1   y M 2   n O z C x :M 3   w   (I);
         wherein M 1  is selected from Sc 3+ , Y 3+ , La 3+ , Sm 3+ , Gd 3+ , Tb 3+ , Pm 3+ , Er 3+ , Lu 3+ , and combinations thereof; M 2  is selected from Al 3+ , In 3+ , Ga 3+ , and combinations thereof; M 3  is selected from Tm 3+ , Bi 3+ , Tb + , Ce 3+ , Eu 3+ , Mn 3+ , Er 3+ , Yb 3+ , Ho 3+ , Gd 3+ , Pr 3+ , Dy 3+ , Nd 3+ , and combinations thereof; and 0.45≦x/n≦0.75, 0.54≦y/n≦0.6, 0.002&lt;w/n≦0.06, and 0.9≦z/n≦1.5. An illumination device including a light emitting element and the aforesaid fluorescent material is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese patent application no.102101132, filed on Jan. 11, 2013.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a fluorescent material and an illuminationdevice using the fluorescent material.

2. Description of the Related Art

Nichia Corporation started to produce white light emitting diodes (whiteLEDs) since 1996. U.S. Pat. No. 5,998,925 discloses a light emittingdevice that generates white light and that comprises a blue lightemitting diode (blue LED) having a wavelength ranging from 450 nm to 470nm as an illuminating unit, and a Cerium-doped fluorescent material(Y₃Al₅O₁₂:Ce³⁺, also known as YAG:Ce³⁺), wherein Cerium is used as anactivator. Part of blue light emitted from the illuminating unit isabsorbed by YAG:Ce³⁺ and converted into yellowish light with arelatively broader emission spectrum (the peak wavelength being around580 nm). Because massive yellow light irradiated by YAG:Ce³⁺ is capableof stimulating both red light and green light photoreceptors in humaneyes, and the rest of blue light emitted from the blue light LEDstimulates blue light photoreceptors, white light could be seen my humaneyes.

However, such combination of blue LED and YAG fluorescent material hasseveral drawbacks including low color rendering index (Ra) owing to lackof red light, lower light emitting efficiency with increasing operatingtemperature, and poor thermal stability of illuminated light induced byhigh power light sources.

In order to alleviate the aforesaid drawbacks, many researchers havefocused on adding silicon (Si) element into the composition of YAG.Silicon compound fluorescent materials, in which Al³⁺ is replaced bySi⁴⁺, have drawn more attention due to higher thermal and chemicalstabilities, stronger absorption in UV zone, high purity and low cost,and abundant supply with respect to silicon or silicate materials.

US Patent Application Publication No. 2010/0142182 discloses anillumination system, comprising a light emitting device which includes afirst phosphor layer, and a second phosphor layer which is separatedfrom the light emitting device. The first phosphor layer includes afluorescent material which contains silicon and nitrogen elements andwhich is represented by the following formula:(Y_(1-α-β-a-b)Lu_(α)Gd_(β))₃(Al_(5-u-ν)Ga_(w)Si_(v))O_(12-y)N_(w):Ce_(a)³⁺Pr_(b) ³⁺);wherein 0≦α<1, 0≦β<1, 0<(α+β+a+b)≦1, 0≦u<2, 0≦ν<2, 0<a<0.25, and0<b<0.25.

This fluorescent material has been modified based on the YAG structure.However, drawbacks of this silicon-containing fluorescent materialinclude low bearing temperature, low stability, and relatively highbrightness which causes over stimulation and results in fatigue of humaneyes after exposure over a long period of time. Also, although nitrogenelement has also been added to raise the sintering temperature, thefluorescent material still only has a sintering temperature ofapproximately 1500° C. Besides, the bearing temperature and stabilityare still insufficient and the color rendering index (Ra) of themodified fluorescent material is about 80%. Moreover, higher quantity ofthe fluorescent material is needed in the illumination system.

Therefore, there is a need in the art to provide a fluorescent materialthat has high bearing temperature, high color rendering index, goodthermal stability, and more natural light emission to avoid overstimulation of human eyes.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide afluorescent material with desirably high bearing temperature and highcolor rendering index (Ra), and an illumination device including theaforesaid fluorescent material.

According to one aspect of this invention, a fluorescent material isrepresented by the following formula (I):M¹ _(y)M² _(n)O_(z)C_(x):M³ _(w)  (I);

wherein M¹ is selected from the group consisting of Sc³⁺, Y³⁺, La³⁺,Sm³⁺, Gd³⁺, Tb³⁺, Pm³⁺, Er³⁺, Lu³⁺, and combinations thereof; M² isselected from the group consisting of Al³⁺, In³⁺, Ga³⁺, and combinationsthereof; M³ is selected from the group consisting of Tm³⁺, Bi³⁺, Tb³⁺,Ce³⁺, Eu³⁺, Mn³⁺, Er³⁺, Yb³⁺, Ho³⁺, Gd³⁺, Pr³⁺, Dy³⁺, Nd³⁺, andcombinations thereof; and 0.45≦x/n≦0.75, 0.54≦y/n≦0.6, 0.002<w/n≦0.06,and 0.9≦z/n≦1.5

According to another aspect of the invention, an illumination devicecomprises a light emitting element, and a fluorescent layer that isformed on the light emitting element. The fluorescent layer includes thefluorescent material mentioned above, and is capable of absorbing lightemitting from the light emitting element.

This invention has the following effects:

a) the fluorescent material is capable of emitting specific light indesired ranges of wavelengths by altering different elements in thefluorescent material;

b) the fluorescent material does not comprise silicon elements, and partof the oxygen elements in the fluorescent material have been replaced bycarbon elements, whereby thermal stability and bearing temperature areincreased accordingly via covalent bonding structure of the carbonatoms; and

c) light emitted from the illumination device of this invention is morenatural and has higher color rendering index (Ra).

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiments of this invention, with reference to the accompanyingdrawings, in which:

FIG. 1 is a partly cross-sectional view of a preferred embodiment of afluorescent material and an illuminating device according to thisinvention;

FIG. 2 is a graph illustrating relative emission spectra of Example 12and Comparative Example 2;

FIG. 3 is a spectrum of Example 14 and Comparative Example 3;

FIG. 4 is a chromaticity coordinate diagram of Example 4;

FIG. 5 is a chromaticity coordinate diagram of Comparative Example 4;and

FIG. 6 is a graph describing degradation of light emission intensity ofExample 5 and Comparative example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a preferred embodiment of an illumination device 1according to the present invention is shown to include a light emittingelement 11, and a fluorescent layer 12 that is formed on the lightemitting element 11. The fluorescent layer 12 includes a fluorescentmaterial, and is capable of absorbing light emitted from the lightemitting element 11 and emits light by photoluminescence effect.

Preferably, the light emitting element 11 includes a chip containing,for example, aluminum (Al), gallium (Ga), nitrogen (N), phosphorus (P),and combinations thereof. More preferably, the light emitting element 11is a LED chip emitting purple, blue, or green light.

Preferably, light emission spectrum of the light emitting element 11 hasa peak wavelength ranging from 350 nm to 500 nm.

Preferably, the fluorescent material of the fluorescent layer 12 isformed on the light emitting element 11 via vapor deposition method.More preferably, the fluorescent material forms a thin film on the lightemitting element 11, and the thin film has a smooth surface.

According to the present invention, a fluorescent material of thefluorescent layer 12 is represented by the following formula (I):M¹ _(y)M² _(n)O_(z)C_(x):M³ _(w)  (I);

wherein M¹ is selected from the group consisting of Sc³⁺, Y³⁺, La³⁺,Sm³⁺, Gd³⁺, Tb³⁺, Pm³⁺, Er³⁺, Lu³⁺, and combinations thereof; M² isselected from the group consisting of Al³⁺, In³⁺, Ga³⁺, and combinationsthereof; M³ is selected from the group consisting of Tm³⁺, Bi³⁺, Tb⁺,Ce³⁺, Eu³⁺, Mn³⁺, Er³⁺, Yb³⁺, Ho³⁺, Gd³⁺, Pr³⁺, Dy³⁺, Nd³⁺, andcombinations thereof; and 0.45≦x/n≦0.75, 0.54≦y/n≦0.6, 0.002<w/n≦0.06,and 0.9≦z/n≦1.5.

Therefore, when n=5, 2.25≦x≦3.75, 2.7≦y≦3, 0.01<w≦0.3, and 4.5≦z≦7.5.

Preferably, M¹ and M³ are different, i.e., they cannot be the same.

When the activator M³ of the fluorescent material comprises Tm³⁺ orBi³⁺, the fluorescent material illuminates blue light. When theactivator M³⁺ comprises Tb³⁺ or Ce³⁺, the fluorescent materialilluminates yellow-green light. When the activator M³ comprises Eu³⁺ orMn³⁺, the fluorescent material illuminates red light. The activator(M³⁺) of the fluorescent material not only correlates to the wavelengthof emitted light but also intensifies the luminescence effect of thefluorescent material.

Preferably, w/n ranges from 0.002 to 0.06. When w/n is less than 0.002,the luminous intensity is insufficient. On the other hand, when w/n isgreater than 0.06, the wavelength of emission light would be increased,which results in lower luminous intensity.

Preferably, the fluorescent material is selected from the groupconsisting of Y_(2.98)Al₅O_(7.5)C_(2.25):Tm_(0.02),Y_(2.95)Al₅O₆C₃:Bi_(0.05), Y_(2.94)Al₅O₆C₃:Tb_(0.06),Y_(2.95)Al₅O_(7.5)C_(2.25):Ce_(0.05), Y_(2.95)Al₅O₆C₃:Ce_(0.05),Y_(2.95)Al₅O_(4.5)C_(3.75):Ce_(0.05), Y_(2.95)Al₅O₆C₃:Mn_(0.05),Y_(2.75)GaAl₄O₆C₃:Mn_(0.25), Y_(2.94)Al₅O_(4.5)C_(3.75):Bi_(0.06),Y_(2.94)Al₅O_(4.5)C_(3.75):Tm_(0.06),Y_(2.94)Al₅O_(4.5)C_(3.75):Ce_(0.04)Tb_(0.02),Y_(2.95)Al₅O_(4.5)C_(3.75):Mn_(0.05),Y_(2.95)Ga₅O_(4.5)C_(3.75):Mn_(0.05), Y_(2.94)Al₅O₆C₃:Bi_(0.06),Y_(2.94)Al₅O₆C₃:Mn_(0.06), Y_(2.94)Al₅O₆C₃:Ce_(0.06),Lu_(1.72)Gd_(1.2)Al₅O₆C₃:Ce_(0.05)Pr_(0.03),Lu_(1.72)Er₁Ga₅O_(4.5)C_(3.75):Mn_(0.25)Dy_(0.03),Lu_(1.92)Sc₁Al₅O₆C₃:Ce_(0.05)Yb_(0.03),Sm_(1.92)La₁Al₅O₆C₃:Ce_(0.05)Ho_(0.03),Y_(2.32)Gd_(0.6)In₁Al₄O₆C₃:Ce_(0.05)Nd_(0.03), andLu_(1.95)Pm₁Al₅O₆C₃:Ce_(0.05).

Preferably, the emission wavelength for the fluorescent material rangesfrom 380 nm to 700 nm. When M³⁺ comprises Tb³⁺, Er³⁺, Yb³⁺ or Ho³⁺, theemission wavelength ranges from 380 nm to 535 nm. When M³⁺ 0 comprisesGd³⁺, Pr³⁺, Dy³⁺, or Nd³⁺, the emission wavelength ranges from 535 nm to700 nm.

Preferably, the fluorescent material has an excitation wavelengthranging from 250 nm to 500 nm.

Preferably, the fluorescent material has a particle size ranging from 5nm to 20 μm.

The fluorescent material can be produced by, but is not limited to,solid-state reaction method, sol-gel reaction method, orco-precipitation method.

Preferably, the fluorescent material is produced by the solid-statereaction method. Because of its relatively simple process, it may beeasily applied in manufacturing large quantities of the fluorescentmaterial. More preferably, the sintering temperature used in thesolid-state reaction method is 1800° C., and temperature of reduction is1500° C.

EXAMPLES

Source of Chemicals

1. Bismuth (III) oxide (Bi₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

2. Barium fluoride (BaF₂): commercially available from ACROS Organics,99.9% of purity, reagent grade.

3. Thulium (III) oxide (Tm₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

4. Cerium (IV) oxide (CeO₂): commercially available from ACROS Organics,99.9% of purity, reagent grade.

5. Ammonium bicarbonate (NH₄HCO₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

6. Manganese dioxide (MnO₂): commercially available from ACROS Organics,99.9% of purity, reagent grade.

7. Yttrium (III) oxide (Y₂O₃): commercially available from ACROSSOrganics, 99.9% of purity, reagent grade.

8. Aluminum oxide (Al₂O₃): commercially available from ACROS Organics,99.9% of purity, reagent grade.

9. Bismuth (IV) oxide (BiO₂): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

10. Terbium (III, IV) oxide (Tb₄O₇): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

11. Gallium (III) oxide (Ga₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

12. Gadolinium (III) oxide (Gd₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

13. Lutetium (III) oxide (Lu₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

14. Erbium (III) oxide (Er₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

15. Dysprosium (III) oxide (Dy₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

16. Praseodymium (III, IV) oxide (Pr₆O₁₁): commercially available fromACROS Organics, 99.9% of purity, reagent grade.

17. Scandium (III) oxide (Sc₂O₃) commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

18. Ytterbium (III) oxide (Yb₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

19. Samarium (III) oxide (Sm₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

20. Holmium (III) oxide (Ho₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

21. Neodymium (III) oxide (Nd₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

22. Promethium (III) oxide (Pm₂O₃): commercially available from ACROSOrganics, 99.9% of purity, reagent grade.

23. Barium magnesium aluminate (BaMgAl₁₀O₁₇, also known as BAM):commercially available from Nemoto & Co. Ltd.

24. Yttrium aluminum garnet (also known as YAG): commercially availablefrom Nemoto & Co. Ltd.

25. Europium (III)-doped Yttrium aluminum garnet (also known as YAG:Eu):commercially available from Nemoto & Co. Ltd.

26. Yttrium carbide (Y₄C₃): synthesized from Y₂O₃ and C under an argongas atmosphere ranging from 1200° C. to 1800° C.

27. Aluminum carbide (Al₄C₃): synthesized from Al₂O₃ and C under anargon gas atmosphere ranging from 1200° C. to 1800° C.

28. Cerium carbide (Ce₄C₃): synthesized from CeO₂ and C under an argongas atmosphere ranging from 1200° C. to 1800° C.

28. Gallium carbide (Ga₄C₃): synthesized from Ga₂O₃ and C under an argongas atmosphere ranging from 1200° C. to 1800° C.

EXAMPLE Example 1 (E1)

Preparation of fluorescent material: 33.65 grams of Y₂O₃ (precursor forM¹), 0.39 grams of Tm₂O₃ (precursor for M³), 20.39 grams of Al₂O₃(precursor for M²), 5.4 grams of Al₄C₃ (precursor for M²), and 2.9 gramsof BaF₂ as a flux agent were mixed together to form a mixture. Themixture was disposed in a crucible, followed by heating to 1650° C. with5° C./min increasing rate and calcining for 24 hours under a nitrogengas atmosphere. The reaction product was then cooled to room temperaturewith 5° C./min decreasing rate, followed by pulverizing, washing,drying, and sieving using a #400 mesh sieve. After reducing at 1500° C.for 12 hours under a reducing atmosphere of nitrogen gas and hydrogengas (85%/15% by volume), a fluorescent powder of Example 1 was obtained.The ingredients and the amounts of the ingredients for Examples 1 areshown in Table 1.

Example 2˜22 (E2˜E22)

The methods for preparing fluorescent materials of Examples 2 to 22 werethe same as that of Example 1, except for the ingredients and theamounts of the ingredients. The ingredients and the amounts of theingredients for Examples 2 to 22 are shown in Table 1.

Comparative Example 1˜4 (CE1˜CE4)

Fluorescent powders for Comparative Examples 1 to 3 were commerciallyavailable and were Y_(2.95)Ce_(0.05)Al₅O₁₂, Y_(2.9)Eu_(0.1)Al₅O₁₂, andBAM, respectively. A fluorescent powder of Comparative Example 4,Y₃Al₂O_(7.5):Ce, was obtained using the same method as that ofExample 1. Ingredients and amounts of the ingredients for ComparativeExample 4 can also be found in Table 1.

[Photoluminescence Test]

The fluorescent powder of Example 1 was excited by purple light with a400 nm peak wavelength, and emission spectrum thereof was measured byvirtue of photoluminescence effect. The fluorescent powder of Example 1emits blue light with a 460 nm peak wavelength (shown in Table 2).Photoluminescence tests for Examples 2 to 22 and Comparative Examples 1to 4 were performed as well. The colors and peak wavelengths ofexcitation light and emission light for Examples 2 to 22 and ComparativeExamples 1 to 4 are also found in Table 2.

TABLE 1 Ingredient (g) Precursor compound M¹ M² M³ flux Formula (g) (g)(g) agent Exp. E1 Y_(2.98)Al₅O_(7.6)C_(2.26):Tm_(0.02) Y₂O₃ Al₂O₃ Tm₂O₃BaF₂ 33.65 g 15.29 g 0.39 g 2~3 g Al₄C₃ 10.8 g E2Y_(2.95)Al₅O₆C₃:Bi_(0.06) Y₂O₃ Al₂O₃ Bi₂O₃ BaF₂ 33.31 g 5.1 g 1.16 g 2~3g Al₄C₃ 14.4 g E3 Y_(2.94)Al₅O₆C₃:Tb_(0.06) Y₂O₃ Al₂O₃ Tb₄O₇ BaF₂ 33.19g 5.1 g 1.12 g 2~3 g Al₄C₃ 14.4 g E4Y_(2.95)Al₅O_(7.5)C_(2.25):Ce_(0.06) Y₂O₃ Al₂O₃ CeO₂ BaF₂ 33.31g 15.29 g0.87 g 2~3 g Al₄C₃ 10.8 g E5 Y_(2.95)Al₅O₆C₃:Ce_(0.06) Y₂O₃ Al₂O₃ CeO₂BaF₂ 33.31 g 5.1 g 0.87 g 2~3 g Al₄C₃ 14.4 g E6Y_(2.95)Al₅O_(4.5)C_(3.76):Ce_(0.06) Y₂O₃ Al₄C₃ CeO₂ BaF₂ 33.31 g 18 g0.87 g 2~3 g E7 Y_(2.95)Al₅O₆C₃:Mn_(0.05) Y₂O₃ Al₂O₃ MnO₂ BaF₂ 33.31 g5.1 g 0.43 g 2~3 g Al₄C₃ 14.1 g E8 Y_(2.75)GaAl₄O₆C₃:Mn_(0.26) Y₂O₃Ga₂O₃ MnO₂ BaF₂ 31.06 g 9.37 g 2.17 g 2~3 g Al₄C₃ 14.4 g E9Y_(2.94)Al₅O_(4.5)C_(3.75):Bi_(0.06) Y₂O₃ Al₄C₃ Bi₂O₃ BaF₂ 33.19 g 18 g1.4 g 2~3 g E10 Y_(2.94)Al₅O_(4.5)C_(3.75):Tm_(0.06) Y₂O₃ Al₄C₃ Tm₂O₃BaF₂ 33.19 g 18 g 1.16 g 2~3 g E11 Y_(2.95)Al₅O_(4.5)C_(3.75):Ce_(0.06)Y₂O₃ Al₄C₃ CeO₂ BaF₂ 33.31 g 18 g 0.87 g 2~3 g E12Y_(2.95)Al₅O_(4.5)C_(3.75):Mn_(0.06) Y₂O₃ Al₄C₃ MnO₂ BaF₂ 33.31 g 18 g0.43 g 2~3 g E13 Y_(2.95)Ga₅O_(4.5)C_(3.75):Mn_(0.05) Y₂O₃ Ga₄C₃ MnO₂BaF₂ 33.31 g 40.8 g 0.43 g 2~3 g E14 Y_(2.94)Al₅O₆C₃:Bi_(0.06) Y₂O₃Al₄C₃ Bi₂O₃ BaF₂ 33.19 g 18 g 1.4 g 2~3 g E15 Y_(2.94)Al₅O₆C₃:Mn_(0.06)Y₂O₃ Al₄C₃ MnO₂ BaF₂ 33.19 g 18 g 0.52 g 2~3 g E16Y_(2.94)Al₅O₆C₃:Ce_(0.06) Y₂O₃ Al₄C₃ CeO₂ BaF₂ 33.19 g 18 g 1.04 g 2~3 gE17 Lu_(1.72)Gd_(1.2)Al₅O₆C₃: Lu₂O₃ Al₂O₃ CeO₂ BaF₂ Ce_(0.05)Pr_(0.03)34.22 g 5.1 g 0.87 g 2~3 g Gd₂O₃ Al₄C₃ Pr₆O₁₁ 21.75 g 14.4 g 0.51 g E18Lu_(1.72)Er₁Ga₃O_(4.5)C_(3.75): Lu₂O₃ Al₄C₃ Mn₂O₃ BaF₂Mn_(0.25)Dy_(0.03) 34.22 g 18 g 2.17 g 2~3 g Er₂O₃ Dy₂O₃ 19.13 g 0.56 gE19 Lu_(1.92)Sc₁Al₅O₆C₃: Lu₂O₃ Al₄C₃ CeO₂ BaF₂ Ce_(0.05)Yb_(0.03) 38.2 g14.4 g 0.87 g 2~3 g Sc₂O₃ Al₂O₃ Yb₂O₃ 7.57 g 5.1 g 0.59 g E20Sm_(1.92)La₁Al₅O₆C₃: La₂O₃ Al₄C₃ CeO₂ BaF₂ Ce_(0.05)Ho_(0.03) 16.29 g14.4 g 0.87 g 2~3 g Sm₂O₃ Al₂O₃ Ho₂O₃ 33.48 g 5.1 g 0.57 g E21Y_(2.32)Gd_(0.6)In₁Al₄O₆C₃: Y₂O₃ In₂O₃ CeO₂ BaF₂ Ce_(0.05)Nd_(0.03)26.19 g 13.88 g 0.87 g 2~3 g Gd₂O₃ Al₄C₃ Nd₂O₃ 10.88 g 14.4 g 0.51 g E22Lu_(1.96)Pm₁Al₅O₆C₃:Ce_(0.05) Lu₂O₃ Al₂O₃ CeO₂ BaF₂ 38.8 g 5.1 g 0.87 g2~3 g Pm₂O₃ Al₄C₃ 16.89 g 14.4 g Comparative Example CE1Y_(2.95)Ce_(0.05)Al₅O₁₂ Commercial Product CE2 Y_(2.9)Eu_(0.1)Al₅O₁₂Commercial Product CE3 BAM Commercial Product CE4 Y₃Al₂O_(7.5):Ce Y₂O₃Al₂O₃ CeO₂ BaF₂ 33.3 g 10.2 g 0.87 g 2~3 g Note: “—” represents “none”

TABLE 2 Excitation Emission Wavelength Wavelength (nm) (nm) FormulaColor color Exp. E1 Y_(2.98)Al₅O_(7.5)C_(2.25):Tm_(0.02) ~400 460 PurpleBlue E2 Y_(2.98)Al₅O₆C₃:Bi_(0.05) ~400 450 Purple Blue E3Y_(2.94)Al₅O₆C₃:Tb_(0.06) ~400 520 Purple Green E4Y_(2.93)Al₅O_(7.5)C_(2.25):Ce_(0.05) 440~480 530 Blue Yellow-Green E5Y_(2.85)Al₅O₆C₃:Ce_(0.05) 440~480 530 Blue Yellow-Green E6Y_(2.95)Al₅O_(4.5)C_(3.75):Ce_(0.05) 440~480 530 Blue Yellow-Green E7Y_(2.95)Al₅O₆C₃:Mn_(0.05) 440~480 650 Blue Red E8Y_(2.75)GaAl₄O₆C₃:Mn_(0.25) 440~480 675 Blue Red E9Y_(2.94)Al₅O_(4.5)C_(3.75):Bi_(0.06) ~400 455 Purple Blue E10Y_(2.94)Al₅O_(4.5)C_(3.75):Tm_(0.06) ~400 450 Purple Blue E11Y_(2.35)Al₅O_(4.5)C_(3.75):Ce_(0.06) 440~480 530 Blue Yellow-Green E12Y_(2.95)Al₅O_(4.5)C_(3.75):Mn_(0.05) 440~480 650 Blue Red E13Y_(2.95)Ga₅O_(4.5)C_(3.75):Mn_(0.05) 440~480 673 Blue Red E14Y_(2.94)Al₅O₆C₃:Bi_(0.06) ~400 450 Purple Blue E15Y_(2.94)Al₅O₈C₃:Mn_(0.06) 440~480 650 Blue Red E16Y_(2.94)Al₅O₈C₃:Ce_(0.06) 440~480 530 Blue Yellow-Green E17Lu_(1.72)Gd_(1.2)Al₅O₆C₃: 450~490 540 Ce_(0.06)Pr_(0.83) BlueYellow-Green E18 Lu_(1.72)Er₁Ga₅O_(4.5)C_(3.76): 450~490 675Mn_(0.25)Dy_(0.03) Blue Red E19 Lu_(1.92)Sc₁Al₅O₆C₃: 450~490 525Ce_(0.05)Yb_(0.03) Blue Yellow-Green E20 Sm_(1.92)La₁Al₅O₆C₃: 450~490535 Ce_(0.85)Ho_(0.03) Blue Yellow-Green E21 Y_(2.32)Gd_(0.6)In₂Al₄O₆C₃:450~490 550 Ce_(0.05)Nd_(0.03) Blue Yellow E22Lu_(1.95)Pm₁Al₅O₆C₃:Ce_(0.05) 440~480 530 Blue Yellow-Green ComparativeExample CE1 Y_(2.95)Ce_(0.05)Al₅O₁₂ 450~490 530 Blue Yellow-Green CE2Y_(2.9)Eu_(0.1)Al₅O₁₂ 400 620 Purple Red CE3 BAM 400 450 Purple Blue CE4Y₃Al₂O_(7.5):Ce 400~490 N/A Purple AND Blue

As shown in Table 2, the fluorescent powder of Comparative Example 1,Y_(2.95)Ce_(0.05)Al₅O₁₂, is excited by blue light and emits yellow lightwith 530 nm peak wavelength; Y_(2.9)Eu_(0.1)Al₅O₁₂ of ComparativeExample 2 is excited by purple light and emits red light with 620 nmpeak wavelength. This reveals that different co-activators (M³) in thefluorescent powders result in different excitation and emission peakwavelengths.

From Examples 4 to 6, it is shown that an increase in carbon content anda decrease in oxygen content in the fluorescent powders do not affectpeak wavelength of emission spectrum. The peak wavelengths of emissionspectrum are primarily related to the species of activators M³ influorescent materials. In these examples, when M³ comprises Tm³⁺ orBi³⁺, the fluorescent material emits blue light. When M³ comprises Tb³⁺or Ce³⁺, the fluorescent material emits green, yellow, or yellow-greenlight. When M³ comprises Mn³⁺, the fluorescent material emits red light.When M³ in the fluorescent material comprises Tb⁺, Yb³⁺ or Ho³⁺, thepeak wavelength of emission spectrum of the fluorescent material rangesfrom 520 nm to 535 nm. When M³ of fluorescent material comprises Pr³⁺,Dy³⁺, or Nd³⁺, the peak wavelength of emission spectrum of thefluorescent material ranges from 540 nm to 675 nm.

FIG. 2 shows relative emission spectra of the fluorescent powders ofExample 12 (Y_(2.95)Al₅O_(4.5)C_(3.75):Mn_(0.05)) and ComparativeExample 2 (YAG:Eu³⁺), each of which is excited by purple light with 400nm peak wavelength. The results show that the fluorescent powder ofExample 12 has stronger photoluminescence intensity as compared to thatof Comparative Example 2.

FIG. 3 shows the spectra of the fluorescent powders of ComparativeExample 3 (BAM) and Example 14 (Y_(2.94)Al₅O₆C₃:Bi_(0.06)). When thefluorescent powder of Comparative Example 3 is excited by purple lightwith a 400 nm peak wavelength, the emission peak wavelength is around450 nm (blue light), and the average number of photons emitted perfrequency in spectrum is 446.9. When the fluorescent powder of Example14 is excited by purple light with a 400 nm peak wavelength, theemission peak wavelength is around 450 nm (blue light), and the averagenumber of photons emitted per frequency in the spectrum is 701.1. Theresults show that the fluorescent powder of Example 14 has betterilluminating efficiency than that of Comparative Example 3.

It is noted that the fluorescent powder of Comparative Example 4(Y₃Al₂O_(7.5):Ce) is a white powder, and has different structure fromother conventional YAG phosphors (Y₃Al_(3˜5)O_(9˜12)). FIG. 4 is a CIEchromaticity coordinate diagram for Comparative Example 4, which shows ablue light output when the fluorescent material of Comparative Example 4is excited by blue light with a peak emission wavelength of 450 nm. Thisindicates that the fluorescent material of Comparative Example 4 cannotbe excited by blue light.

As shown in FIG. 5, when the fluorescent powder of Example 4 is excitedby blue light with a peak emission wavelength of 450 nm, thechromaticity coordinates of Example 4 are located in zone of whitecolor. This indicates that the fluorescent powder of Example 4 emitsyellow-greenish light, and the emitted yellow-greenish light mixes withpart of blue light to form white light. The major difference in formulabetween the fluorescent powder of Example 4 and the fluorescent powderof Comparative Example 4 resides in the atom numbers of aluminum (Al)and carbon (C). The difference in the atom numbers of aluminum andcarbon between Example 4 and Comparative Example 4 is (Al₄C₃)_(0.75),which causes phosphor emission for the fluorescent powder of Example 4.Based on formula (I), the difference in the atom numbers of aluminum andcarbon between the fluorescent materials of this invention andconventional materials could range from 2.25 to 3.75.

FIG. 6 is a graph showing degradation of light emission intensity withchange of temperature for the fluorescent powders of Example 5(Y_(2.95)Al₅O₆C₃:Ce_(0.05)) and of Comparative Example 1(Y_(2.95)Ce_(0.05)Al₅O₁₂). FIG. 6 shows that degradation level of lightemission intensity for Example 5 is less than that of ComparativeExample 1. It is suggested that the less degradation might be attributedto the covalent bond of carbon elements, which improves thermalresistance for the fluorescent powder of Example 5.

In the aspect of color rendering index, the conventional YAG fluorescentmaterials have color rendering index (Ra) of around 80%. Some otherconventional fluorescent materials, which are modified by substitutingaluminum element of YAG with silicon element, have similar colorrendering index (Ra) of around 80% since the structures thereof aresimilar to that of YAG. However, the color rendering index of thefluorescent materials of this invention might be greater than 85%, whichis better than that of the conventional YAG or YAG-modified materials.

To sum up, by altering the species and the amounts of elements in thefluorescent material of this invention, the fluorescent materialsirradiating different colors of light can be obtained. Also,substitution of part of oxygen (O) atoms with carbon (C) atoms in thefluorescent material of this invention would enhance the bondingstrength through covalent bonds of carbon atoms. The fluorescentmaterial of this invention has a sintering temperature of around 1800°C. and has good thermal resistance. Moreover, superior color renderingindex can be achieved in this invention.

While the present invention has been described in connection with whatare considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation andequivalent arrangements.

What is claimed is:
 1. A fluorescent material wherein said fluorescentmaterial is selected from the group consisting ofY_(2.98)Al₅O_(7.5)C_(2.25):Tm_(0.02), Y_(2.95)Al₅O₆C₃:Bi_(0.05),Y_(2.94)Al₅O₆C₃:Tb_(0.06), Y_(2.95)Al₅O_(7.5)C_(2.25):Ce_(0.05),Y_(2.95)Al₅O₆C₃:Ce_(0.05), Y_(2.95)Al₅O_(4.5)C_(3.75):Ce_(0.05),Y_(2.95)Al₅O₆C₃:Mn_(0.05), Y_(2.75)GaAl₄O₆C₃:Mn_(0.25),Y_(2.94)Al₅O_(4.5)C_(3.75):Bi_(0.06),Y_(2.94)Al₅O_(4.5)C_(3.75):Tm_(0.06),Y_(2.94)Al₅O_(4.5)C_(3.75):Ce_(0.04)Tb_(0.02),Y_(2.95)Al₅O_(4.5)C_(3.75):Mn_(0.05),Y_(2.95)Ga₅O_(4.5)C_(3.75):Mn_(0.05), Y_(2.94)Al₅O₆C₃:Bi_(0.06),Y_(2.94)Al₅O₆C₃:Mn_(0.06), Y_(2.94)Al₅O₆C₃:Ce_(0.06),Lu_(1.72)Gd_(1.2)Al₅O₆C₃:Ce_(0.05)Pr_(0.03),Lu_(1.72)Er₁Ga₅O_(4.5)C_(3.75):Mn_(0.25)Dy_(0.03),Lu_(1.92)Sc₁Al₅O₆C₃:Ce_(0.05)Yb_(0.03),Sm_(1.92)La₁Al₅O₆C₃:Ce_(0.05)Ho_(0.03),Y_(2.32)Gd_(0.6)In₁Al₄O₆C₃:Ce_(0.05)Nd_(0.03), andLu_(1.95)Pm₁Al₅O₆C₃:Ce_(0.05).
 2. The fluorescent material of claim 1,wherein said fluorescent material has an emission wavelength rangingfrom 380 nm to 700 nm.
 3. The fluorescent material of claim 1, whereinsaid fluorescent material has an excitation wavelength ranging from 250nm to 500 nm.
 4. An illumination device, comprising: a light emittingelement; and a fluorescent layer that is formed on said light emittingelement, that includes a fluorescent material of claim 1, and that iscapable of absorbing light emitting from said light emitting element. 5.The illumination device of claim 4, wherein said fluorescent materialhas an emission wavelength ranging from 380 nm to 700 nm.
 6. Theillumination device of claim 4, wherein said fluorescent material has anexcitation wavelength ranging from 250 nm to 500 nm.